The Secrets of Solar Flares

By: Susie77 , 8:10 PM GMT on September 19, 2011



The Secret Lives of Solar Flares

Play ScienceCast VideoJoin Mailing ListSept. 19, 2011: One hundred and fifty two years ago, a man in England named Richard Carrington discovered solar flares. 
Secret Lives (sunspots, 200px)
Sunspots sketched by R. Carrington on Sept. 1, 1859. © R. Astronomical Society. [more]

It happened at 11:18 AM on the cloudless morning of Thursday,
September 1st, 1859. Just as usual on every sunny day, the 33-year-old
solar astronomer was busy in his private observatory, projecting an
image of the sun onto a screen and sketching what he saw. On that
particular morning, he traced the outlines of an enormous group of
sunspots. Suddenly, before his eyes, two brilliant beads of white light
appeared over the sunspots; they were so bright he could barely stand to
look at the screen.

Carrington cried out, but by the time a witness arrived minutes
later, the first solar flare anyone had ever seen was fading away. 

It would not be the last. Since then, astronomers have recorded
thousands of strong flares using instruments ranging from the simplest
telescopes in backyard observatories to the most complex spectrometers
on advanced spacecraft.  Possibly no other phenomenon in astronomy has
been studied as much. 

After all that scrutiny, you might suppose that everything about
solar flares would be known.  Far from it.  Researchers recently
announced that solar flares have been keeping a secret.

“We’ve just learned that some flares are many times stronger than
previously thought,” says University of Colorado physicist Tom Woods who
led the research team. “Solar flares were already the biggest
explosions in the solar system—and this discovery makes them even
bigger.”
Secret Lives (splash, 558px)
Click to view a ScienceCast video about the late phase of solar flares. [Youtube]

NASA’s Solar Dynamics Observatory (SDO), launched in February
2010, made the finding:  About 1 in 7 flares experience an
“aftershock.”  About ninety minutes after the flare dies down, it
springs to life again, producing an extra surge of extreme ultraviolet
radiation. 

“We call it the ‘late phase flare,’” says Woods.   “The energy in
the late phase can exceed the energy of the primary flare by as much as a
factor of four.”

What causes the late phase? Solar flares happen when the magnetic
fields of sunspots erupt—a process called “magnetic reconnection.”  The
late phase is thought to result when some of the sunspot’s magnetic
loops re-form.  A diagram prepared by team member Rachel Hock of the University of Colorado shows how it works. 

The extra energy from the late phase can have a big effect on
Earth.  Extreme ultraviolet wavelengths are particularly good at heating
and ionizing Earth’s upper atmosphere.  When our planet’s atmosphere is
heated by extreme UV radiation, it puffs up, accelerating the decay of
low-orbiting satellites.  Furthermore, the ionizing action of extreme UV
can bend radio signals and disrupt the normal operation of GPS.   

SDO was able to make the discovery because of its unique ability
to monitor the sun’s extreme UV output in high resolution nearly 24
hours a day, 7 days a week.  With that kind of scrutiny, it’s tough to
keep a secret--even one as old as this.

The original research of Woods et al may be found in the Oct. 1, 2011, issue of the Astrophysical Journal.



Author: Dr. Tony Phillips | Credit: Science@NASA

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Sometimes I complain about the earthly weather, but mostly I like to post about astronomy and space events. Hope you enjoy the articles.

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